There is a demand for non-destructive detection of deterioration or abnormality occurring in a structure such as a building. For example, in inspection of a bridge as a structure, an inspector visits an inspecting road on the bridge, performs detection of an abnormality by visual inspection, hammering sound inspection (contact inspection), or the like and identifies a part to be repaired with priority. In such contact inspection, an abnormality is determined relying on a sound that the inspector listens to, and thus an abnormality cannot be determined quantitatively. Such contact inspection is labor-intensive resulting in a low work efficiency and tends to cause increased cost.
In general, in a structure abnormality detection system, measuring devices such as, typically, accelerometers are regularly arranged in a structure, the vibration mode is derived from the measuring results obtained when a local vibration is given to the structure, the degree of a change is calculated from the vibration mode obtained when the structure is normal, and thereby an abnormality of each structure is determined.